High Electron Mobility Transistor (HEMT) based hydrogen sensor for deep-surface applications: Effect of Air and N2 atmosphere

Abstract

The detection of hydrogen in the Earth's deep underground poses a major challenge due to the lack of oxygen and continuous changes in environmental conditions. An innovative class of hydrogen gas sensors based on AlGaN/GaN High Electron Mobility Transistors (HEMTs) with Platinum (Pt) gates as a functionalization layer, has been developed and optimized for geo-sensing. The study investigated the sensor characteristics using two carrier gases to simulate underground conditions, namely air (with 20 % O2) and N2 (with 0 % O2), across a range of temperatures from 50 °C to 300 °C and with hydrogen concentrations varying from 25 ppm to 400 ppm. The detection limit was found to be approximately 1 ppm of hydrogen in the atmospheric air. The gas sensor transduction is based on the modification of the conductivity of a 2-Dimensional Electron Gas (2DEG). In this study, the principle was investigated using two gases, O2 and H2, with different electronegativities relative to platinum. The adsorption competition between H2 and O2 on platinum was evaluated, and this allowed the calculation of the ratio of thermodynamic adsorption constants between these two gases.